apple spraying experiments in i915. 179 



Arsenate oe Lead Atone for Catyx and Later 

 Applications. 



The use of a strong fungicide for the first foliage spray fol- 

 lowed by double strength arsenate of lead alone, as applied to 

 plots 3 and 4 in 191 5, has been tried for two successive seasons. 

 Again, as in 1914, conditions were such that it is impossible to 

 draw conclusions relative to the advantages derived from the 

 use of the strong fungicidal spray instead of arsenate of lead 

 alone for the first application. This is due to the fact that 

 omitting the first application of standard dilution lime-sulphur 

 entirely on plot 2 was not followed by any increase in scab as 

 compared with plot 1 which was sprayed three times with the 

 same material. Apparently scab control in 191 5 came largely 

 from the two later applications. Also the differences in amounts 

 of scab recorded on plots 3 and 4 when compared with plot 5, 

 sprayed with arsenate of lead alone, are within the limits of 

 experimental error. However, the results obtained on plots 3 

 and 4 tend to conform those secured on 5 and similar plots of 

 previous years relative to the fungicidal action of arsenate of 

 lead. They also add to the evidence that, under the climatic 

 conditions which existed in 191 5 as well as in 19 14, the first 

 fungicidal spray application had little to do in the prevention 

 of apple scab. 



Again, as in 1914, an application of 3-3-50 bordeaux mixture 

 on plot 4 before the flower buds opened resulted in leaf injury 

 and increased fruit russeting. It is difficult to explain why some 

 of this injury should occur. As has already been pointed out 

 the injury was not confined to those leaves already formed 

 when the bordeaux mixture was applied, and the amount of 

 russeted fruit, as compared with the check, was increased about 

 9 per cent. Since the apple fruit is morphologically an enlarged 

 and thickened calyx tube it is evident that a strong spray ap- 

 plied before the blossom buds open may and does reach tis- 

 sues which later develop into the the skin of the fruit. Hence, 

 there is a possibility that it might cause injury then which would 

 appear as russeting later. Attention is called to the fact, how- 

 ever, that as is shown below an application of winter strength 

 lime-sulphur to plot 8 at an earlier date when the blossom buds 

 were still all surrounded and protected by young leaves led to 

 somewhat more russeting of the fruit than was recorded upon 



